Distillation method and apparatus



Feb. 6, 19450 cs. T. KOHMANET AL DISTILLATION METHOD AND APPARATUS Filed Dec. 17, 1942 I s Sheets-Sheet 1 .0. r KOHMAN WVENTORS CHPRESCOTTJR.

A TTORNEV Feb. 6, 1945. G. T. KOHMAN ET AL D ISTILLATION METHOD AND APPARATUS Filed Dec. 17, 1942 3 Sheets-Sheet 2 lanllii FIG. 4

6 a. 7'.KOHMAN gjr.HPRESCOTTJR.'

A T TORNE V 945 G. T. KOHMAN ET'AL 68,

DISTILLATION METHOD AND APPARATUS Filed Dec. 17, 1942 s Sheets-Sheet s ATTQRNFL,

Patented Feb. s, 1945 DISTILLATION METHOD AND APPARATUS Girard T. Kohman, Summit, and Charles H. Prescott, Jr., Boonton, N. J assigno'rs to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 17, 1942, Serial No. 469,370

18 Claims. ('01. 202- 49) This application relates to distillation processes and apparatus, and more particularly to method and apparatus involving the use of mechanical energy for distilling'an impure liquid to obtain a purified liquid. I

The mechanical stills; or apparatus for distilling through the agency of mechanica1 energy,

provided by the present invention may be compact and portable if desired, are simple in operation; and do not require accurat control of operating conditions. Apparatus of the portable .manually operated type embodying the invention may be extremely useful for providing potable water from sea water for shipwrecked mariners. Apparatus of the power driven, continuously operating, type embodying the invention maybe advantageously employed for general distillation purposes and may be e ployed to particular adstate, for conducting the air from the chamber F v, containing the purified liquid back to the chamber containing the purified liquid. The apparatus may be manually operable orpower driven. If it is power driven, means may be advantageously provided for continuously supplying impure liquid to the apparatus, for removing excess impure liquid and waste concentrate, and for revantage in locations where power is, available but heat cannot be employed, as in submarines.

The present invention provides a method of distillation, and apparatus operating according to the method, in which a stream of air or other suitable gas is first contacted with a body of the impure liquid which is to be distilled so that the air becomes laden with vapor from said liquidy the vapor-laden air is compressed by a mechanical pump sufllciently to cause liquid to condense from the compressed air under conditions such that as much as possible and in any event most of the resulting heat of condensation passes to the body of impure liquid and raises its vapor pressure; the condensed liquid is collected; the compressed air is expanded through a throttling valve so that the expanded air'is in the unsaturated condition; and the air is again contacted with the body of liquid to become laden with vapor therefrom. The above cycle of operations on the circulating stream of air is continuously repeated during operation of the apparatus. A

In general, the apparatus embodying the invention comprises a chamber adapted to contain the impure liquid; a' chamber adapted to contain the purified liquid; means, advantageously a separating wall of heat conductive material betweenthe chambers, to conduct heat from the chamber adapted to contain the purified liquid to the chamber containing the impure liquid; "a suitable pump adapted to remove vapor-ladenair from the chamber containing the impure liquid and to compress the air'sufficientlyto cause vapor to condense therefrom into the liquid while the heat of condensation passes to the body of impure liq uid; and means, including valve means through which the air is expanded tothe unsaturated moving th purified liquid.

The present invention will be explained herein after in connection with the accompanying drawings in which:

' Fig. 1 is a sectional elevation, generally corresponding to line l-.I of Fig. 2 of a manually. op-

erable mechanical still embodying the invention;

Fig. 2 is 'a cross-sectional elevation, along th line 22 of Fig. l, of said still; Fig. 3 is a sectional elevation, generally corresponding to line 3-3 of Fig. 4, of a power driven mechanical still embodying the present invention,

this figure being to a scale smaller than that of I Figs. 1 and 2;

Fig. 4' is a cross-sectional elevation along line.

4-4 of Fig. 3 of the apparatus of said figure and to the same scale; and

Fig. 5 is a sectional elevation of the heat exchanger corresponding to line 5-5 of Fig. 4,- but to a larger scale than that of said figure.

, The apparatus of Figs. 1 and 2 is a portable hand .operable mechanical still embodying the invention, which is useful as life-boat equipment for the purpose of providing a source of potable water from sea water for shipwrecked mariners.

For convenience, it will be described hereinafter as adapted to the production of potable water from sea water. The apparatus of these figures comprises a pump cylinder I rigidly mounted in a container 2 which inturn is rigidly mounted in a container 3, a supporting spider l which is fixed, as by spot welding, to the interior of the container 3 being provided to support andlocate the container 2. Containersl and 3 are sealed, as by brazing or weldingat points 5 and 6 .to provide liquid and air-tight joints. The cylinder l and container 2 cooperate to provide an annular chamber 1 which surrounds the cylinder l and is adapted to contain the body 8 of sea water. The containers 2 and 3 are arranged to provide a chamber I in which is collectedthe distilled water.

The walls of cylinder l and container 2 are shown as formed of metal, which is' desirable because of its strength and heat conduction qualities.

Cylinder! contains a piston l3 mounted On a which is adjustable by thumb nut 32.

ton I3 is provided'with .a fiap I6 of a suitable material, such as leather, to provide a tightseal between the piston is and the wall of the cylinder I. and with a valve, formed of a loosely mounted plate I! and openings I8, which valve opens to permit gas to pass from the portionof the cylinder above the piston to the portion of the cylinder below the piston on the upstroke of the piston and which closes to permit compression of the gas below the piston on the downstroke of the piston. The piston rod I4 is shown as operating through a seal I9 mounted in the upper end closure 2I of the cylinder to prevent escape of substantial amounts of gas past the piston rod.

' In the illustrated apparatus, tube 22 provides communication between the upper-end of the sea 2,868,665 rod l4 provided with actuating handle I 5. Pissubstantial pressure which, however, need not necessarily be a high pressure. The valve 23 ad- .vantageously is adjusted to open when the pressure in' cylinder I is only slightly greater than that in chamber 9, so that the pressure developed in the portion of the cylinder I below the piston and in the chamber 9 is substantially equal as the piston continues to move downwardly. As

pressure is developed in the cylinder, some condensation of the vapor carried by the air may occur in the cylinder. and a considerable portion of the heat of condensation developed may thus pass through the wall I3 of the cylinder into the body 8 of sea water surrounding the cylinder I. As the piston I3 approaches the lowermost position, indicatedby the broken lines I5, the mixwater chamber 1 and the upper end of the interior of cylinder I. Check valve 23 is shown in the apparatus of Figs. 1 and 2as providing communication between the bottom of the cylinder I and the interior of distilled water chamber 9: The illustrated valve comprises a ball 24 which is urged by spring 25 against the outlet of passage 26 from The-passage 26 is closed by the ball 24 on the upstroke of the piston I 3 and is opened by the pressure developed on the downthe cylinder I.

stroke of the piston. Preferably, the valve is adiusted so that it opens when apressure only slightly greater than that in chamber 9 is developed within the cylinder I. Y

A throttle valve 21 through which the air in vided at the upper portion of chamber 9. The valve 21 shown comprises a needle 28 urged a ainst, a valve seat at the end of the inlet orifice 29 of the valve by a spring 3|, the pressure of The discharge orifice of the valve 2! is connected to a tube 33 which discharges into an annular tube 34 at the bottom of the chamber I containing the sea water. Tube 34 contains perforations 35.

The illustrated apparatus also includes a dis charge tube 38 which extends from the bottom of v the chamber, 9 forc'ontaining distilled water and which is at the top thereof provided with a stop cook 31 and swingabledischarge nozzle 38. Noz- "zle 38 is shown as swung into the non-use position but when itis to be employed it is swung to the position 38. indicated by broken lines. A wooden base 38 which provides both strength and heat insulating properties is provided in the illustrated apparatus. To conserve heat, a thick layer 4i of suitable heat insulating material; such as rock wool or spun glass, is provided at the sides tureof air, fog and condensed liquid is forced out through valve 23 into the chamber 2. The condensed liquid falls to the lower portion II of the chamber 9 where it is collected, and the air containing uncondensed vapor passes upwardly to chamber 3'discharges and freely expands is prothe upper portion II] of chamber 9, in the space between the walls of containers 3 and 2,'w'here further condensation of the vapor in the air occurs. As large a portion as possible of the heat 'of condensation developed is thus caused to pass through the wall of container 2 into the body 8 of sea water. When the air reaches the top of chamber 9, it has lost a considerable portion of its-water vapor, although it still contains some vapor. ,The air expands through valve 21 substantially to atmospheric pressure. The spring 3 [of the valve is adjusted so that the valve maintains in the chamber '9 and cylinder I a suitable pressure. The pressure developed in the apparatus largely depends upon the dimensions of the-apparatus; that is, since the amount of physical energy normally available to operate the apof the apparatus,.and a heat insulatin cover 42 of similar material is provided at the top of the apparatus. The cover 42 may be removed by drawing both it and the pump handle 45 upwardlyto provide access to the upper portion of the apparatus, as: for adjustment purposes, ad-

dition of sea water, or removal of distilled water from the apparatus. A removable plug 43 is shown to provide access to the chamber] for addition 'or removal of sea water or cleaning purposes. I a

In Operation of the apparatus-of Figs. land-2, air which isladen and usually saturated with vapor from the body 8 of impure liquid is drawn into the cylinder I through tube 22 when the Piston I3 is urged downwardly by handle I 5. On

the upstroke, such vapor-laden air passes through the valveopenings I8 intothe space in the cylinder I below the piston I3. On the. nextdownstroke of the piston, the air is compressed. to a paratus is limited, the pressure developed is largely determined by the piston area. It may lie between 4 and 40 pounds per square inch above atmospheric presure and for advantageous operating conditions should be about 10 pounds per square inch above atmospheric pressure. The nature of the expansion through valve 21 is such that substantially no change in the heat content or temperature occurs as the air passes through the valve, although a large increase in entropy occurs. Thus the air is not cooled substantially,

culation of the stream of air, vapor is carried by the air from the body of sea water, and is condensed and collected as a purified liquid.

The condensation of the vapor and the passage of most of its heat of condensation into the body 8 of sea water cause the vapor pressure of the sea water to rise and thus increase the emciency of the apparatus. During operation of the apparatus, the temperature orthe internal portions of the apparatus and the liquid therein rises to a l point determined by rate of heatloss due to heat conduction, radiation and other causes. In an 'efiiciently designed apparatus, the temperature may approach the boiling point of water. As the temperature increases and the air in the system expands, some of the air escapes from the system past the seal I9 around the piston rod I4.

From time to time, the cover 42 may be removed, the nozzle 38 swung to the discharge position 28', and purified liquid be discharged from the still. Pressure may be built up in the still by pumping to facilitate discharge. For this purpose it is also advantageous to close entirely the valve 21 by turning thumb screw 32.

The method of operation is essentially an isothermal one, since there are no substantial temperature changes at any step.

"The apparatus .of Figs. 3 to5'inclusive, 'is a power driven, substantially continuously operating mechanical still, embodying the invention and is useful for general distillation purposes or in installations where mechanical power is available but heat is not available, or its use is unfeasible I the nature of the distilling operation, it is advanfirstembodimentof the invention. Because of tageous that the pump be a positive displacement pump. A rotary positive displacement pump, such as the Roots pump shown, is advantageous because it provides a positive. displacement and continuous flow without excessive air turbulence, and a large capacity at moderate pressure.

While a reciprocatory piston pump might be em- I ployed, such a pump is characterized by the disadvantage that it causes considerable discontinuity or turbulence of flow. A centrifugal blower type pump is in general undesirable because of the difiiculty of obtaining the required pressures with such a pump.

Pump 62 is driven-by a-suitable source of power, not shown, applied to shaft. The pump 'discharges through tube 64 into the lower portion of inner chamber 45. Air from saidchamber discharges and expands through throttling valve 65.

This valve comprises needle 66 pressed .by spring 61 which is adjustably controlled by nut 68 to maintain a .suitable pressure ofthe air in the "chamber 45.

65 be adjusted to provide a "pressure in chamber It is advantageous that the valve I of approximately four to five pounds per square inner chamber 45 and surrounding it, an outer annularchamber 46, the two chambers being separated by a heat conductive wall 41 of metal.

The inner chamber 45 which is adapted to contain and have condensed therein the purified water is provided with a plurality of bubble plates which serve to facilitate condensation of vapor. separation of liquid from the 'aif, and conduction of heat into the outer chamber 46. Each of the illustrated bubble plates 48 is formed of a lower annular member 49 of metal or other material of good heat conductivity which is fixed to the inner I surface of wall 41, as by pressing, brazing, or welding to form a heat conductive joint and to form an annular trough 5| adapted to contain liquid.

Associated with each plate 48 is an upper cap plate 52 supported by rods 53.to which it is fixed and having a downwardly turned edge 54 extending into trough 5|, as shown. A sufficient-num-- ber of bubble plates 48 are present to provide good heat conductivity and removal of liquid fromthe air.

'Similar bubble plates 55 are present in outer chamberv 46. Eachbubble plate 55 comprises a.

lower annular member 56 mounted on the outer surface of wall 4'! and fixed thereto as by pressing, brazing or welding. to form a heat conductive chamber.

joint. Each plate 55 is shaped to provide a trough '51 for containing liquid. A cooperating upper plate 58. which is provided for each ate .56. is similarly mounted on the outer wall 9. of the chamber 46 and is shaped with a downwardly projecting edge 60 extending into trough 51 as shown. The purpose ofbubble plates 56 in the outer chamber 46 is to promote the addition of vapor to th air passing through chamber 46 and to promote the conduction of heat to the impure water.

Tub'e'BI of chamber 46 is connected to the inlet side of a pump 62 which is removed from the chamber 4B containing the impure water-in the sense that there is no direct metallic connection between the pump and said chamber for conducting heat from the pump to the chamber, as is present in the communicating with the upper portion inch. The air, after expansion throughvalve 65,

passes through tube 69 into the lower portion of outer chamber 46. Impure water, such as salt water, is supplied to the upper portion of outer chamber 41 through tube'II which in turn is. supplied through heat exchanger I2; I

The illustrated heat exchanger I2 comprises a coil of tubing 13 of relatively large diameter containing therein two lengths of tubing "and 15 of smaller diameter, as is shown to advantage in Fig. 5. The space between the inside of'tube I3 and the outside of tubes 14 and 15 conducts the impure water supplied to the system. This liquid is supplied to the heat'exchangerin the illustrated apparatus by a suitable pump 16, the inletpipe 11 towhich communicates with a suitable source of impure water. Pump 16 is shown as being driven by pulleys 18, I9 and belt from speed reduction means 8| which, in turn, is driven from pump 63 by pulleys 82, 83' and-belt 84. Tube I4 of heat exchanger 12 is connected to the bottom portion of outer chamber 46 and conducts away excess impure liquid supplied to said chamber. Tube I5 is connected to the lower portion ofinner chamber 45 and conducts away purified liquid which has been collected in said The liquids being removed from the system by passing through tubes 14 and 15 are at elevated temperature, and give up heat in heat exchanger 12,, to the impure water being supplied to the system, with a consequent conservation of heat and entropy. A suitable float valve 85' is' shown in the, chamber 46 to control the removal of the. excess impure water from said chamber and to prevent the level of theliquid in the chamber from rising, beyond a pre determined amount. Preferably, the valve 85 is such that it provides a continuous flow of liquid and not a sharp cut-oil" of the flow, since a constant flow of liquid is advantageous for efiicient operation of heat exchanger". A similar valve 86 .is shown asprovided in chamber 45 to control the now of purified water through'tube I5 and to control the level ofithe water in chamber '45. It is also advantageous for emcient operationof the heat exchanger I2 that valve'tfi provide a continuous flow of water.

To conserve heat more e'fliciently, it is desirable that the inlet pump I6 and at least the 4- aseaees lower portion of the heat exchanger 12, both of the total heat content or temperature of the air,

- which contain liquids at relatively low temperaalthough it causes a considerable increase in tures, be covered with heat insulating material, the entropy. The air, therefore, is not cooled not shown. substantially, if at all. The expanded air, which As shown in Figs. 3 and 4, the apparatus is 5 is in the unsaturated condition for its temperaenclosed in a layer 81 of a suitable heat insuture andpressure, pass through tube 69 to the lating material such as rock wool or the like, lower portion of chamber 46. 'The air in chamand is provided with a removable cover 88 of ber i6 passes upwardly in a tortuous path similar heat insulating material. Such heat inthrough and between the bubble plates 55.- In' 'sulation adds to the efficiency of the apparatus 10 this passage, the air intimately contacts theimby conserving heat. In the illustrated appapure water bybubbling-throughthe water conratus, moreover, a vent tube 89 is provided to tained in the trough 51 and passing in contact equalize the. pressure between the atmosphere with the water trickling downwardly through the and the interior of the chamber 46 and to perchamber. When the air reaches the upper pormit the escape of air from the system as the tion of chamber 46, it is laden with vapor, usually system becomes heated and the air therein exbeing fully saturated. v pands during operation. The cycle of operations upon the air is repeat- An auxiliary heating means 9|, shown as an edly performed during operation of the appaelectrical heater, is provided in the lower por a-- .ratus so that as the air circulates through the 7 portion of the chamber 45. .Meanwhile, a large ,tion' of the outer chamber 46. This heating system, it conduc s v por f m the y f immeans may be advantageously employed to heat pure water, is compressed to cause condensation the impure water in the system at the comof the vapor therefrom with passage of heat of mencement of operation of "the apparatus -.to. condensation to the body of i pu liquideX- bring the apparatus to its full operating efllpanded and again contacted with the impure ciency sooner than wouid otherwise be the case. a the condensed pu fi d q d being Such heating means may, of course, be employed lected in the lower portion of the chamber 45. during operation of the apparatus but in gen- The collected purified water is continuously re- ;eral'heating during operation is unnecessary. movedfrom the syste through V ve and In operation of the apparatus of Figs. 3to 5 tube 75, and the excess impure water is removed inclusive, impure liquid, as sea water, is drawn u h. Valve a e although interthro h th t b 11 by pump 16 d passed mittent removal is possible if desired. through heat exchanger 12 and tube 1|, from The cycle of operat on se n y n i 0- which it is discharged into .theupper portion of thermal cycle since there is no substantial temchamber 46. The liquid trickles downwardly peratu chan e in ny p r n f h y l over 2 and. through the bubble plates 55, some of -35 H w th mp tu of e pparatus and it r j aining in the troughs 51. The excess liqof the liquid gradually increases and approaches uld c llects in the lower portion of chamber 48 he boiling temperature of the liquid, the upper and discharges through valve 85 andtube 14 limit of the temperature being determined y through heat exchange 12. As indicated above t rate of t losses f m th apparatus.

this operationadvantageously in a continuous '40 Both forms of'apparatus describedaboveare, operation although it may be intermittent if as is apparent, simple, inexpensive and compact desired. in construction. They are eflective in permit- Air laden','and advantageously saturated with, ting the recovery of purified liquid from impure vapor from the impure water isdrawn from the liquids so y through the xpen iture of meupper portion of chamber 46 through tube 6| tehani eal energy. Moreoventhe method of operinto the inlet of pump 62. The vapor-laden air ation of each of .the described forms of apparatus is compressed by pump 62 and passed through is such that no critical operating conditions are tube 64 into'the lower portion of chamber 45. In required. In this respect, the method and appasome cases some condensationmight occurin rat'us of the, present invention are superior to pump 63, but in general, because of the speed prior methods and apparatus.

of travel and heat of compression, the vapor Each of the above-described embodiments of laden air is discharged into chamber 45 bef r a the. invention is illustrative only, and it is appp iable condensation occurs. parent that various modifications may be made The air travels upw rdl 1n chamber pass- 7 therein and in their modes of operation, and

ing through the tortuous paths between the 65 that other forms of apparatus and other modes Plates and 52 of the h pl 48 aha of operation may be devised without departing.

bung through the liquid which 9 in trough from the spirit of the invention. For example As s f s g g E 53 whereas the invention was discussed in connec pOr con enses rom e. and epo as a liquid on the inner surface of the wall 41 and '00 22 figggl gg ggg gggi ggi gg ig on the bubble plates 48. The liquid collects. in

the trough 5| of each bubble plate, overflows vention may be applied e distillation of uids other than water. M reover, whereas the therefrom ahd eventually collects in the'lower invention was disclosed in connection with the use of air as the vapor-carrying gas, it is apparent that other suitable gases may be employed for these purposes; obviously the vaporportion of the heat of condensation of the vapor 05 being condensed passes through heat conductive wall 41 into the liquid-in chamber, 46, the passage of heat being facilitated by the bubble A rying gas should be one which does not itself" plates I condense under the pressures employed during when the reachesth-upper portion f the process and which is capable of carrying chamber 45 it has lost most, .if not all, of its Vapors of the liquid to he distilled- In the excess liquid vapor. It discharges through valve pend d claims e, term is u e fl S} in which it is expanded to substantially atineludesuch gases as Well as aih J 3 mospheric pressure. Th We on the ai'r. It is intended that the patent shall cover, through said valve does not appreciably change 76 by suitable expression in the appended claims,

1. The process for distilling a liquid comprising contacting a portion of .a circulating esSentially constant mass ofair with a body of the liquid to be distilled under conditions which cause the air to become laden with vapors of the liquid; compressing the vapor-laden air sufficiently to cause vapor carried by the air to condense; condensing the vapor carried by said compressed vapor-laden air while its pressure is greater than the pressure ofthe vapor-laden air prior to compression and while saidvaporladen air is out of contact with said body of liquid but under conditions such that substantially all of the heat of condensation of the condensate passes into said body of liquid, meanwhile collecting the condensate; expanding said air from which vapor has been condensed to substantially its original pressure before compression to cause said air tobe in the unsaturated state; and contacting substantially all of said expanded air with said body of liquid to be distilled to commence repetition of the cycle.

2. The process for distilling a liquid comprising contacting a portion of a circulating essentially constant mass of air with a body of the liquid to be distilled 'under conditions which cause the air'to become'laden with vapors of the liquid; compressing the vapor-laden air sufficiently to" cause vapor carried by the air to condense; condensing the vapor carried by said compressed vapor -laden air .while its pressure is' greater than the pressure of the vapor-laden air prior to compression and while said vapor-laden air is out of contact with said-body of liquid cause the air to become laden with vapors of the liquid; compressing the vapor-laden air sufficicntly to cause vapor carried by the air to condense; condensing the vapor carried by said compressed vapor-laden air while its pressure is greater than the pressure of the vapor-laden air prior to compression and while said vapor-laden air is out of contact with said body of liquid but under conditions such that substantially all of the heat of condensation of the condensate passes into said body of liquid; expanding said air from which vapor has been condensed to substantially Y its original pressure before compression to cause said air to be in the unsaturated state; contacting substantially all of said expanded air with said body of liquid to be distilled to commence repetition of the cycle; continuously collecting thecondensate resulting from condensation of the vapor from the air; and continuously adding liquid to said body of liquid which is to be distilled.

-5. The process for distilling a liquid comprising contacting a portion of a circulating essentially constant mass of air with a body of the liquid to be distilled under conditions which cause the air to become laden with vapors'of :the liquid; compressing the vapor-laden air sufficicntly to cause'vapor carried by the air to conbut under conditions such that substantially all of the heat of condensation of the condensate passes into said body of liquid, meanw-hile collecting the condensate; rapidly expanding said air from which vapor has been condensed, without substantial cooling of the air, to substantially its original pressure before compression to cause said air to be in an unsaturated state; and contacting substantially all of said expandedair with said body of liquid to be distilled to commence repetition of the cycle.

3. The process for distilling a liquid compris r stream of air an essentially isothermal cycle of ing repeatedly performing upon a circulating operations coniprising'adding to the stream of air vapors from a body of the liquid to be distilled; compressing the vapor-laden, air sufficiently to cause to to condense; condensing the vapor carried by said compressed vapor-laden air while its pressure is greater than-the pres-v sure of the vapor-laden air prior to compression and while said vapor-laden air is out of contact with said body of liquid but under conditions such that substantially all of the heat of condensation of the condensate passes into said body of liquid, meanwhile collecting the condensate; rapidlyexpanding the air from which vapor has been condensed, without substantial cooling of said air, to substantially its original pressure before compression to cause said air to be in the unsaturated state; and again adding to-substantially all of said air vapors from .said bodyof liquid to be distilled, whereby the cycle of operationsjs recommenced.

4. The process for distilling a liquid comprising contacting a portion' of a circulating essentially constant mass of air with a body of the liquid ,to be distilled under conditions which dense; condensing the vapor carried by said compressed vapor-laden air while its pressure is greater than the pressure of the vapor-laden air prior to compression and while said vapor-laden air is out of contact with said body of liquid but under conditions such that substantially all of the heat of condensation of the condensate passes into said body of liquid; expanding said air from which vapor has been condensed to substantially its original pressure before compression to cause said air to be in the unsaturated state; contacting substantially all of said expanded air with said body of liquid to commence repetition of the Y cycle; collecting and withdrawing the condensate resulting from the condensation of vapor from the air; and adding liquid to the, body of liquid to be distilled, said added liquid being' preheated by out-of-contact and c ounterfiow'heatexchange with the condensate being withdrawn.'

vapor; and means, including valve means which maintains an elevated pressure of the vaporladen air in said second chamber and which relieves the pressure of the air as it passes through said valve means, for conducting sub'-' stantially all the air from said second chamber to said first chamber in which it again becomes laden with vapor from said liquid which is to'be distilled.

'7. Distillation apparatus comprising a first chamber adapted to contain'liquid which is to, be distilled; a second chamber adapted to contain liquid condensate resulting from distillation and separated from said'first chamber by a heat conductive wall; a pump adapted to withdraw'f "from saidrfirst chamber air laden with ,vapor I from said liquid which is to be distilled, to compress said vapor-laden air, and to pass said compressed vapor-laden air to the interior of the means, for conducting substantially all the air from said second chamber to said first chamber in which the air again becomes laden with vapor from said liquid which is to be distilled.

8.,Distillation apparatus comprising a first chamber adapted to contain liquid which is to be distilled; a pump adapted to withdrawvfrom said first chamber air laden with vapor from said liquid which is to be distilled and to compress said vapor-laden air; a second chamber adapted to receive the compressed vapor-laden air from said pump and to have condensed therein into a liquid condensate vapor from said compressed air; means for transferring from said second chamber to said first chamber heat of condensation of said condensed vapor; means, including valve means which maintains an elevated pressure of the vapor-laden air in said second chamber and which relieves the pressure of the air as it passes through said valve means, for conducting substantially all the air from said second chamber to said first chamber in which it again becomes laden with vapor from said liquid which 7 is to be distilled; and means in said first chamber ficiently to cause vapor'from said compressed air to condense into a liquidcondensate while heat of condensation passes through said wall intosaid first chamber; and means, including valve means which maintains an elevated pressure of the vapor-laden air in said second chamber and which relieves the pressure of the air as it passes through said valve means, for conducting sub-1 stantially all the air from said second chamber to said first chamber in which the air again becomes laden with vapor from said liquid which is to be distilled.

10. Distillation apparatuscomprising a pump cylinder; a chamber surrounding the pump cylinder which'is adapted to contain liquid to be distilled in contact with'the exterior of said ber in which the air again becomes laden with vapor from said liquid to be distilled.-

11. Distillation apparatus comprising a pump cylinder, a chamber surrounding the pump cylinder which is adaptgdto contain liquid to be distilled in contact with the exterior of saidpump cylinder, the interior of which chamber communicates with the interior of said pump cylinder; a reciprocatory piston in said pump cylinder adapted to withdraw from the interior I of said chamber air laden with vapor fro'mthe 'said .liquid and to compress such vapor-laden air sufilciently to cause vapor to condense therefrom into a liquid condensate; a second chamber into which said compressed air and said condensate pass from said cylinder and in which said condensate collects; and means, including". valve means for releasing the pressure of the air, for conducting the air'from said second communicates with the interior of said pump,

cylinder; 9, reciprocatory piston in said pump cylinder adapted to withdraw from the interior of said chamber air laden with vapor from said liquid and to compress such air sufiiciently to cause vapor to condense therefrom into a liquid condensate; a container surrounding said pump cylinder and having a-heat conductive wall in contact with said liquid to be distilled in said chamber, into which container said compressed air is urged by said piston and in which vapor condenses from said compressed air while heat of condensation passes through said wall into said liquid to be distilled in said chamber; and means, including valve means for relieving the pressure of the air, for conducting the air from. said container into said chamber in which the air again becomes laden with vapor from said liquid to be distilled.

l3. Distillation apparatus comprising a pump cylinder; a chamber surrounding said pump cylinder which is adapted to contain liquid to be distilled in contact with the exterior 01' said pump cylinder, the interior of which chamber" pump cylinder/the interior of which chamber communicates with the interior of the pump cylinder; a. reciprocatory piston in said pump cylinder adapted to withdraw from the interior or said chamber air laden with vapor from the said liquid and to compress'such vapor-laden air sufliciently'to cause vapor to condense from said air into a liquid condensate with-passage of heat of condensation through the cylinder wallinto said liquid to be distilled in said chamber; "and means, including valve means for re-. lieving the pressure of the air, for conducting the air from said pump cylinder into said chamcylinder; a reciprocatory piston in said pump cylinder adapted to. withdraw from interior of said chamber air laden with vapor -from said liquid and to compress such air sufliciently to cause vapor to condense therefrom into a liquid condensate; a container surrounding said chamber which contains said liquid to be. distilled and having a heat conductive wall in contact with said liquid in'said chamber, into which side of said chamber adapted to withdraw from said first chamber air laden with vapor from said liquid and to compress said vapor-laden air; a second chamber adapted to receive the compressed vapor-laden air from said pump and to condense therein into a liquid condensate vapor from said compressed air; means for transferring from said second chamber to said first chamber heat of condensation of said condensate; and means, including valve means which maintains an elevated pressure of the vaporladen air in said second chamber and which relieves the pressure of the air as it passes through said valve means, for conducting substantially all the air from said second chamber tosaid first chamber in which it again becomes laden with vapor from said liquid to be distilled.

l5. Distillation apparatus comprising a first v chamber adapted to contain liquid which is to be distilled; a power-driven pump located outside of said chamber adapted to withdraw from said first chamber .air laden with vapor from said liquid and to compress said vapor-laden air; a second chamber adapted to receive the compressed air from said pump and to condense therein into a liquid condensate vapor from said compressed air; means for transferring from said second chamber to said first chamber heat of condensation of said condensate; means, in-

ner chamber adapted to contain liquid condensate; an outer chamber surrounding the inner chamber and separated from it by a heat conductive wall adapted to contain liquid which is to be distilled; a power-driven pump located outside of said chambers adapted to withdraw from said outer chamber air laden with vapor,

from said liquid to be distilled, to compress said vapor-laden air and to pass said vapor-laden air to said inner chamber in which vapor condenses from said air into a liquid condensate and from which heat of condensation passes into said liquid to be distilled in the outer chamber; and means, including valve means which maintains the pressure of the vapor-laden air in said inner chamber and which relieves the pressure of the air as it passes through said valve means, for conducting the air from said inner chamber to said outer chamber in which it again becomes laden with vapor from said liquid to be distilled.

17. Distillation apparatus comprising an in-l ner chamber adapted to contain liquid condensate; an outer chamber surrounding the inner chamber and separated from it'by a heat conductive wall adapted to contain liquid which is to be distilled; va power-driven pump located outside of said chambers adapted to withdraw from said outer chamber air laden with vapor from said liquid to be distilled, to compress said vapor-laden air and to pass said vapor-laden air to saidinner chamber in which vapor condenses from said air into a liquid condensate and from which heat of condensation passes into said liquid to be distilled in the outer chamber; means, including valve means which maintains an elevated pressure of the vapor-laden air in said inner chamber and which relieves the pressure of the air as it passes through said valve means, for conducting the air from said inner chamber to said outer chamber in which it again becomes laden with vapor from said liquid to be distilled; means in said outer chamber for bringing the stream of air into intimate contact with said liquid to be distilled; and means in said inner chamber for promoting removal of vapor from the compressed air and conducting heat to the outer chamber.

18. Distillation apparatus comprising an upright inner chamber adapted to contain liquid condensate: an upright outerchamber, surrounding said inner chamber and separated from it by a heat conductive wall, adapted to contain liquid to be distilled; a power-driven rotary positive displacement pump adapted to withdraw from said outer chamber air laden with vapor from said liquid to be distilled, to compress said vapor-laden air and pass it to said inner chamber in which vapor condenses from said air into a liquid condensate and from which heat of condensation passes into said outer chamber; means, -including valve means which maintains an elevated pressure of said vapor-laden air in said inner chamber and which abruptly relieves the pressure of the air as it passes through said valve means, for conducting air from the upper portion of said inner chamber to the lower portion of said outer chamber; means for supplying liquid to be distilled to the upper portion of said outer chamber; means for withdrawing the excess liquid from the lower portion of said outer chambery and means providing an exchange of heat between the liquid being supplied to said outer chamber and the liquid being removed from said chamber.

GIRARD T. KOHMAN; CHARLES H. PREsco'rr, JR. 

